Waniewski Jacek, Kurowska Weronika, Mizerski Jeremi K, Trykozko Anna, Nowiński Krzysztof, Brzezińska-Rajszys Grazyna, Kościesza Andrzej
Interdisciplinary Center for Mathematical and Computational Modelling, Warsaw University, Warsaw, Poland.
Artif Organs. 2005 Aug;29(8):642-50. doi: 10.1111/j.1525-1594.2005.29102.x.
The modified Blalock-Taussig shunt is a palliative operation for some congenital heart diseases. An artificial conduit with antithrombotic surface placed between the subclavian (or innominate) and the pulmonary artery supplies blood to the lungs in defects with decreased pulmonary flow. Clotting of the graft is the main cause of its failure. Stenosis of the arteries is also observed. The objective of the present study was to investigate the flow pattern in the graft to investigate the possibility that clotting is initiated by the stimulation of platelets by high shear stress, and the possible effect of the pathological wall shear stress on the stenosis formation. The model included the left subclavian artery (LSA), the left pulmonary artery (LPA), and the graft. The three-dimensional relative position and size of the arteries was obtained from a CT scan of real anatomy. Four different types of the graft with two different diameters (3 and 4 mm) and two different shapes (straight and curved) of the pipe, and one variable diameter pipe were inserted in the model. A pulsatile flow of 0.81 L/min on average was assumed at the inlet to LSA, and 80% of the flow was directed through the graft. Computer simulations demonstrated a complex flow pattern with eddies and low velocity regions in the arteries at the anastomoses with the graft in all five models. An eddy was also found inside the straight 4 mm graft. A high pathological shear rate was present within the graft, with higher values in the 3 mm grafts. The fractional volume with a high (>2500 L/s) shear rate was between 2.5% and 4.5%, and that with a very high (>7500 L/s) shear rate between 0 and 1.5% of the model volume, and depended on the graft geometry and the phase of the cardiac cycle. Pathologically high (>3.5 Pa) and pathologically low (<1.0 Pa) wall shear stress, which may induce neointimal growth, was found in LSA and LPA. We conclude that the activation of platelets by high shear rate is possible within the graft, followed by their subsequent aggregation in the eddies with a low flow rate. Flow-induced changes of the vessel wall thickness (stenosis) can also appear, especially in the pulmonary artery.
改良布莱洛克 - 陶西格分流术是针对某些先天性心脏病的一种姑息性手术。在锁骨下动脉（或无名动脉）与肺动脉之间放置具有抗血栓表面的人工导管，用于在肺血流减少的缺损中为肺部供血。移植物形成血栓是其失效的主要原因。还观察到动脉狭窄。本研究的目的是研究移植物中的血流模式，以探讨高剪切应力刺激血小板引发凝血的可能性，以及病理性壁面剪切应力对狭窄形成的可能影响。该模型包括左锁骨下动脉（LSA）、左肺动脉（LPA）和移植物。动脉的三维相对位置和大小通过真实解剖结构的CT扫描获得。将四种不同类型的移植物（两种不同直径（3毫米和4毫米）、两种不同形状（直管和弯管）的管道）以及一种可变直径管道插入模型中。假设LSA入口处平均脉动流量为0.81升/分钟，其中80%的血流通过移植物。计算机模拟表明，在所有五个模型中，与移植物吻合处的动脉中存在复杂的血流模式，伴有涡流和低速区域。在直管4毫米移植物内部也发现了一个涡流。移植物内存在较高的病理性剪切速率，3毫米移植物中的值更高。剪切速率高（>2500升/秒）的部分体积占模型体积的2.5%至4.5%，剪切速率非常高（>7500升/秒）的部分体积占模型体积的0至1.5%，这取决于移植物的几何形状和心动周期阶段。在LSA和LPA中发现了可能诱导新生内膜生长的病理性高（>3.5帕）和病理性低（<1.0帕）壁面剪切应力。我们得出结论，移植物内高剪切速率可能激活血小板，随后血小板在低流速的涡流中聚集。血流诱导的血管壁厚度变化（狭窄）也可能出现，尤其是在肺动脉中。
